1. Field of Invention
The present invention relates to an apparatus for removing a sulfur-containing compound contained in a fuel for automobiles between a fuel tank and an injector of an engine or in a gas station fuel tank or a tanker truck, and which is particularly suited for use as an apparatus to be mounted in automobiles.
2. Related Art
A sulfur-containing compound contained in a fossil fuel is a direct contributor of sulfur oxide in exhaust gas after combustion, and is also a contributor to generating particulate matter in the exhaust gas. Furthermore, removal of the sulfur-containing compound before combustion is important to maintain the service life of a catalyst type for removing nitrogen oxide in the exhaust gas.
It has hitherto been considered to be particularly difficult to remove an aromatic sulfur-containing compound such as benzothiophene, dibenzothiophene or the like among sulfur-containing compounds contained in the fossil fuel.
Japanese Unexamined Patent Publication (Kokai) No. 2-235992 describes a method of passing a fuel into a first cellulose filter packed with a chromate compound, as a means for removing impurities such as an aromatic substance in the fuel, and passing the fuel through a second filter filled with water, thereby to remove impurities. However, there is no specific description about removal of a sulfur-containing aromatic compound.
Japanese Unexamined Patent Publication (Kokai) No. 11-9293 describes bacteria capable of decomposing alkylated benzothiophene or alkylated dibenzothiophene. However, there is no specific description about the use of bacteria for removal of a sulfur-containing aromatic compound in a fuel.
Japanese Unexamined Patent Publication (Kokai) No. 10-117799 describes a method of decomposing dibenzothiophene using microorganisms such as Coriolus versicolor. However, there is no description about a specific method of removing dibenzobenzene in a fuel.
It is therefore an object of the present invention to provide an apparatus for efficiently removing a sulfur-containing compound contained in a fossil fuel for automobiles in a comparatively trace amount, especially an aromatic sulfur-containing compound such as benzothiophene, dibenzothiophene or the like before combustion.
As a result of substantial research to solve the problems as described above, the present inventors have found that a sulfur-containing aromatic compound, which could not be removed easily by the method of the prior art, can be efficiently removed by adsorbing a sulfur-containing compound in a fuel, thereby to concentrate the sulfur-containing compound, and chemically oxidizing the concentrated sulfur-containing compound using an oxidizing agent or an oxidation catalyst. Thus, the present invention has been accomplished.
More specifically, the present invention provides a sulfur-containing compound removing apparatus, which is arranged between a fuel tank and an injector of an engine or arranged in a gas station fuel tank or a tanker truck, the apparatus comprising:
(1) a sulfur-containing compound adsorbent for adsorbing the sulfur-containing compound in a fuel;
(2) a sulfur-containing compound oxidizing agent or oxidation catalyst for oxidizing the sulfur-containing compound to form a sulfur-containing oxide, which is immobilized in the sulfur-containing compound adsorbent (1) or coexists with the sulfur-containing compound; and
(3) (3-a) a sulfur-containing adsorbent for adsorbing the sulfur-containing oxide, which coexists with the sulfur-containing compound adsorbent (1) and the sulfur-containing compound oxidation catalyst (2) or arranged at a lower stream thereof; and/or
(3-b) a sulfur-containing oxide salt removing means for removing the sulfur-containing oxide as a salt thereof.
The present invention also provides a sulfur-containing compound removing apparatus, which is arranged between a fuel tank and an injector of an engine or arranged in a tank of a gas station or a tank lorry, the apparatus comprising:
(1) a sulfur-containing compound adsorbent for adsorbing the sulfur-containing compound in a fuel;
(2) a sulfur-containing compound oxidizing agent or oxidation catalyst for oxidizing the sulfur-containing compound to form a sulfur-containing oxide, which is immobilized in the sulfur-containing compound adsorbent (1) or coexists with the sulfur-containing compound;
(3) a microorganism-immobilized carrier in which a microorganism capable of oxidizing the sulfur-containing oxide into a sulfate salt or a sulfite salt has been immobilized, which coexists with the sulfur-containing compound adsorbent (1) and the sulfur-containing compound oxidation catalyst (2) or arranged at a lower stream thereof; and
(4) (4-a) a sulfur-containing adsorbent for adsorbing the sulfur-containing oxide, which coexists with the microorganism-immobilized carrier (3) or arranged at a lower stream thereof; and/or
(4-b) a sulfur-containing oxide salt removing means for removing the sulfur-containing oxide, the sulfate salt or the sulfite salt in the form of an insoluble salt thereof.
The sulfur-containing oxide salt removing means (3-b) or (4-b) is, for example, a filter or porous material which supports an oxide or a salt of an alkali metal or an alkali earth metal.
The sulfur-containing oxide salt removing means (3-b) or (4-b) is, for example, an insoluble sulfate salt filtering-off filter.